feat: Add custom branding functionality with CSS and JSON configuration

- Introduced custom branding CSS styles in `custom-branding.css`.
- Created example JSON configuration for custom branding in `custom-branding.example.json`.
- Implemented branding configuration logic in `BrandingConfig.ts` to normalize and validate branding settings.
- Developed CSS loader to manage loading and unloading of custom stylesheets in `BrandingCssLoader.ts`.
- Added DOM rendering capabilities for branding elements in `BrandingDomRenderer.ts`.
- Defined types and interfaces for branding elements and configurations in `BrandingTypes.ts`.
- Included localization support for German in `de-de.js`.
- Added unit tests for branding configuration, CSS loader, and DOM renderer.
- Validated project structure and static assets with new validation scripts.

config/package-solution.json

@@ -3,22 +3,9 @@
   "solution": {
     "name": "custom-branding-client-side-solution",
     "id": "03a7c4de-e031-4b83-a683-5ca5c364166e",
-    "version": "1.0.4.0",
+    "version": "3.0.0.0",
     "includeClientSideAssets": true,
-    "skipFeatureDeployment": false,
-    "features": [
-      {
-        "title": "Custom Branding extension registration",
-        "description": "Registers the Custom Branding Application Customizer in the host web.",
-        "id": "2eb6deaa-a4a0-40c5-9f15-6bdaff36094f",
-        "version": "1.0.4.0",
-        "assets": {
-          "elementManifests": [
-            "elements.xml"
-          ]
-        }
-      }
-    ]
+    "skipFeatureDeployment": true
   },
   "paths": {
     "zippedPackage": "solution/custom-branding.sppkg"